Design a small disconnect cicuit

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I need a small circuit that can disconnect AC power (means will have a
relay) when it detects freezing on coil. I have a non working
appliance that I want to power up but also include a antifreeze
circuit design so that when it senses ice or freezing on the coils it
powers off/disconnects. can anyone help ? is there any such circuits
available that can do this job ?

 

[JeffM]

[...]appliance[...]so that when it senses ice or freezing on the coils
it powers off/disconnects.

http://www .google.com/search?q=temperature.controller&num=100
Set it to limit at 33F.

 

[ecp]

[...]appliance[...]so that when it senses ice or freezing on the coils
it powers off/disconnects.

http://www .google.com/search?q=temperature.controller&num=100
Set it to limit at 33F.

Some form of direct frost detector perhaps.
Polish a section of the coil to a mirror finish, and then
use an optical reflectance sensor to detect frost formation.

Eric

 

[D from BC]

I need a small circuit that can disconnect AC power (means will have a
relay) when it detects freezing on coil. I have a non working
appliance that I want to power up but also include a antifreeze
circuit design so that when it senses ice or freezing on the coils it
powers off/disconnects. can anyone help ? is there any such circuits
available that can do this job ?

Thermistor + comparator + relay
D from BC

 

[John Fields]

[...]appliance[...]so that when it senses ice or freezing on the coils
it powers off/disconnects.

http://www .google.com/search?q=temperature.controller&num=100
Set it to limit at 33F.

Some form of direct frost detector perhaps.
Polish a section of the coil to a mirror finish, and then
use an optical reflectance sensor to detect frost formation.

 

[John Fields]

I need a small circuit that can disconnect AC power (means will have a
relay) when it detects freezing on coil. I have a non working
appliance that I want to power up but also include a antifreeze
circuit design so that when it senses ice or freezing on the coils it
powers off/disconnects. can anyone help ? is there any such circuits
available that can do this job ?

---
View in Courier:


+12V>-----+-------+---------+--------+----+-----+
| | | | | |
| | | [10k] |K | O------C
[47k] [30k] | | [CR1] [COIL]- - -|
| | +---|--[1M]--+ | | O--> |<--O--NC
| | | | | +-----+ |
| | | | | | +-----------NO
+---+---------+--|+\ | D
| | | | >------+--+-----G 2N7000
[RTH] | [10k]<--+--|-/ U1A | S
| | | | | LM393 | |
+---+ | | | | |K |
| | | | | | [Z15V] +---|+\
| [39k] | [30k][0.1µF]| | | | >
| | | | | | | +---|-/ U1B
[0.1µF]|[0.1µF]| | | | |
| | | | | | | |
GND>--+---+---+---+-----+---+-----------+-------+

RTH is a thermistor with a resistance of 10K at 0C.

 

[Uncle Monster]

I need a small circuit that can disconnect AC power (means will have a
relay) when it detects freezing on coil. I have a non working
appliance that I want to power up but also include a antifreeze
circuit design so that when it senses ice or freezing on the coils it
powers off/disconnects. can anyone help ? is there any such circuits
available that can do this job ?

No need to reinvent the wheel.

http://www.sensata.com/products/controls/ptherm-7bt2.htm

[8~{} Uncle Monster

 

[Fred Bloggs]

I need a small circuit that can disconnect AC power (means will have a
relay) when it detects freezing on coil. I have a non working
appliance that I want to power up but also include a antifreeze
circuit design so that when it senses ice or freezing on the coils it
powers off/disconnects. can anyone help ? is there any such circuits
available that can do this job ?

No need to reinvent the wheel.

http://www.sensata.com/products/controls/ptherm-7bt2.htm

[8~{} Uncle Monster

Those may not work very well with the +/-5oF tolerance on setpoint, not
too mention no standard part number is suitable.

 

[Fred Bloggs]

I need a small circuit that can disconnect AC power (means will have a
relay) when it detects freezing on coil. I have a non working
appliance that I want to power up but also include a antifreeze
circuit design so that when it senses ice or freezing on the coils it
powers off/disconnects. can anyone help ? is there any such circuits
available that can do this job ?

There may be but they will be junk. The best way is to modify the
"sealed system" by including an evaporator pressure regulator set for a
refrigerant saturation pressure corresponding to 33oF. You will need to
know how to pump the system down, make proper flare connections, install
pressure access ports and other fittings, and read something called a
pressure gauge and something called a thermometer. Something like
this:https://pgw100.portal.gases.boc.com...ts/DANFOSS_Evaporator_Pressure_Regulators.asp
The thermostat cutoff is the pussy weakling half-assed wimp way of
handling the problem: the sissy nerd method IOW.